For the cutting of sheet metal or other sheet material, use is commonly made of a machine known as a "nibbler", having one fixed blade and one reciprocating blade, the reciprocating blade co-operating with the fixed blade in a guillotine like manner, and the machine is moved over a work piece so as to create a single shear line. In other nibblers, there are parallel shear lines and a small strip is removed from the workpiece.
A data bank search revealed the following U.S. specifications Nos:
3,143,911 Dickerson PA1 4,074,603 Bengtsson PA1 4,312,610 Burt, and PA1 4,249,309 Karr.
Of those specifications, reference is particularly made to the Dickerson U.S. Pat. No. 3,143,911 and the Bengtsson U.S. Pat. No. 4,074,603. The closest art to the present invention known to the applicant is the Dickerson U.S. Pat. No. 3,143,911 wherein the nibbler body was constituted by a single start helical thread which was arranged to urge an edge of a workpiece against a sharpened bushing edge of a flat workpiece receiving face at right angles to the axis of rotation of the thread.
One of the difficulties encountered with devices of that type is that the thickness of the workpiece is necessarily much less than the gap between the outstanding webs of the thread so that the workpiece can be urged against the roof of the thread, the surface which defines the helical groove bearing downwardly on the upper surface of the workpiece progressively upon rotation but since the workpiece is not inclined at the helix angle there is essentially some impact and consequential deflection of the workpiece.